docs: def onscreen_len(s):
      """
      Calculate the length of a unicode string on screen,
      accounting for double-width characters
  
      """
  
      if sys.version_info < (3, 0) and isinstance(s, str):
          return len(s)
  
      length = 0
      for ch in s:
          length += 2 if unicodedata.east_asian_width(ch) == 'W' else 1
  
      return length